The present invention relates to a removable flexible pipeline in a secondary containment system. More particularly, the invention relates to a method of and a structure for removing a flexible inner pipeline from within an outer pipeline.
In recent years, increased awareness of air and water pollution problems caused by leaking gasoline or other polluting elements has focused attention on ways to detect and prevent such leaking. To this end, double walled piping systems have been developed. For example, in U.S. Pat. No. 4,932,257 (to Webb), a primary pipeline carries gasoline from an underground storage tank to a dispenser, and a secondary pipeline surrounds the primary pipeline to prevent leaking gasoline from contaminating the ground.
In U.S. Pat. Nos. 4,842,163 and 4,971,225 (both to Bravo), a containment box is installed directly below a gasoline dispenser and around a gasoline pump to collect leaks from the dispenser or pump.
In such secondary containment systems, however, it is difficult to effect repairs on the primary pipeline should a leak develop. Often one must not only break ground around the gasoline pump, but also break up the island on which the pump is located to determine where the leak is and to fix it. U.S. Pat. No. 4,971,477 (to Webb et al.) discloses one approach to this problem. In this patent, there is a secondary containment system with a double pipeline formed in segments. Each segment connects two access chambers which extend from ground level to below the pipeline. The ends of an outer pipeline segment connect to fittings built into adjacent chambers, respectively. The ends of an inner pipeline connect to fittings at a position located within adjacent chambers, respectively. The inner pipeline is flexible. When an inner pipeline segment or fitting is in need of repair, the covers of two adjacent chambers are removed and the fittings for the inner pipeline segment are disconnected. Then, that segment is removed from one of the access chambers for repair or replacement.
In the Webb, et al. system, there must be at least two access chambers to remove a flexible inner pipe. Moreover, although Webb, et al. show an access chamber below a gasoline dispenser, the patent does not disclose a way to remove the segment leading to the gasoline dispenser if a leak develops in that segment. One would have to remove the dispenser and perhaps even break up the island on which the dispenser is located. Moreover, Webb et al do not address the situation where a containment box, such as in the Bravo patents, is used, and the flexible pipeline connects to a rigid line at a point below the containment box.